1. Field of the Invention
This invention relates broadly to incorporating radiation-absorbing components into ophthalmic lenses. In a preferred embodiment, this invention relates to methods of tinting contact lenses.
2. Description of the Related Art
A number of radiation-absorbing agents have been incorporated into ophthalmic lenses, especially contact lenses, for a variety of reasons. Two popular types of radiation-absorbing agents include ultraviolet (UV) light-absorbing agents and visible light absorbing agents, i.e., tinting agents. A number of patents have issued and a number of patent applications have been published relating to this technology. Some of these patents and publications are discussed below in order to provide the reader with an understanding of the state of the art.
U.S. Pat. No. 4,157,892, issued to Tanaka, et al. on Jun. 12, 1979, teaches a method of coloring a water-absorbable plastic. The method involves forming a soft contact lens and immersing the lens in an aqueous solution of a diazonium salt at a pH suitable to cause a coupling reaction to form an azoic dye within the lens.
U.S. Pat. No. 4,553,975, issued to Kai Su on Nov. 19, 1985, and U.S. Pat. No. 4,559,059, issued to Kai Su on Dec. 17, 1985, describe polymeric lens materials in which exoskeletal covalent bonds are formed between reactive dyestuffs and monomer units of the polymer backbone. The formation of the covalent bond is effected by contacting the dyestuff formulation with the lens material under basic pH conditions. The dye is bonded to the lens material via ether linkages.
U.S. Pat. No. 4,891,046 issued to Wittman, et al. on Jan. 2, 1990, teaches a process of tinting lenses by impregnating the lens with an aqueous solution of a dichlorotriazine reactive dye and fixing the dye in the lens by immersing the lens in an aqueous alkaline solution.
U.S. Pat. No. 4,929,250, issued to Hung, et al. on May 29, 1990, discloses a method of preparing a UV-absorbing lens by contacting the lens with a solution including an agent having a reactive halotriazine bonded to an aqueous soluble moiety and a UV radiation-absorbing component.
U.S. Pat. No. 5,292,350, issued to Molock, et al. on Mar. 8, 1994, teaches a method of tinting a soft contact lens by (a) polymerizing a mixture of (i) a hydrophilic acrylate monomer and (ii) a water-soluble halotriazine dye to form a lens, then (b) immersing the lens in an aqueous alkali to react the dye with the hydroxyalkyl groups of the acrylate. The dye compound does not possess any functionality which is readily polymerizable with the hydrophilic monomer from which the lens is derived.
European Patent Application Publication No. 0 472 496 A2 teaches a method of forming a tinted lens by (a) applying an ink formulation to a lens mold, (b) allowing the ink formulation to dry, (c) adding lens forming material, (d) forming the lens, and (e) placing the lens in an activating medium.
U.S. Pat. No. 5,480,927, issued to Janssen, et al., on Jan. 2, 1996 teaches a method and composition useful in fabricating radiation-absorbing contact lenses, especially ultraviolet (Uv) and visible (tint) light-absorbing lenses. The raditation-absorber is incorporated into a contact lens in the presence of a buffer which maintains the pH near neutral. Subsequently, the radiation absorber is chemically affixed to the lens by raising the pH to a highly basic level. This process increases the amount of radiation-absorber affixed to the lens.
All of the prior disclosures teach the formation of a lens first, followed by the activation of the reaction between the lens material and the dye material. Activation is followed by extraction of unreacted dye material and activation material from the lens. There remains a need to reduce the processing time, handling, scrap, material usage and equipment required for the preparation of dyed polymeric articles, especially visibility tinted contact lenses.